As disclosed in U.S. Pat. No. 4,670,686, and shown in FIGS. 1 and 2, herein a conventional color CRT 10 has a faceplate panel 12, with a tricolor cathodoluminescent viewing screen 13 on an internal surface thereof, that is sealed to a funnel 14 thereof along an edge 16 of the sidewall of the panel. The CRT 10 has an internal magnetic shield 18 disposed therein proximate an inner surface 20 of the funnel 14. The magnetic shield 18 is fastened by means of a base 19 to a color selection electrode assembly, such as a shadow mask and frame 22 which is attached by mounting studs 24 to the sidewall of the panel 12 and spaced from the screen 13. The inner surface 20 of the funnel 14 has a conductive coating 26 thereon extending along the surface 20 to a predetermined distance from the edge 16. A substantially continuous bowl-like sidewall 27 extends backward from the base 19 of the shield, along the inner surface 20 of the funnel 14, and terminates in a substantially flat rear flange 30. A pair of contact springs 28 are attached to the surface of the flange 30, at the rear of the internal magnetic shield 18, for effecting an electrical connection between the shield and the conductive coating 26. The shield 18 includes an aperture 31 formed through the surface of the flange 30. An indentation or ridge 32 is formed around the flange 30 to prevent improper insertion of the spring 28, as described in the above-referenced patent. As shown in FIG. 2, the springs 28 are located on opposite sides of the flange 30 and are directed parallel to the major axis A--A of the tube 10. A second embodiment of a conventional magnetic shield 18' is shown in FIG. 3. The shield 18' differs from the shield 18 in that V-shaped notches are formed in a sidewall 27' of the shield to extend the aperture 31' in the direction of the major axis A--A. The contact springs 28 are secured to the surface of the flange 30' and extend generally parallel to the minor axis B--B.
Each of the conventional shields 18 and 18' is formed of cold-rolled steel having a thickness within the range of about 0.01 to 0.18 mm. Before the springs 28 are attached, the shields are annealed and blackened to improve their magnetic properties and to reduce reflections. A problem with an internal magnetic shield formed of a continuous sheet of relatively thin steel is that the shield lacks rigidity and is susceptible to handling damage, for example, when the contact springs 28 are affixed to the flanges 30 or 30'. Additionally, it has been determined that a bending force is exerted on the shield from the pressure of the contact springs, when the shield is installed within the funnel 14. This bending force sometimes creates an inflection point or bend at the corners of the shield and, thus, changes the magnetic properties of the shield, or, if severe enough, causes the shield sidewall to collapse sufficiently to intercept a portion of the electron beams. Structural integrity of the magnetic shield can be increased by making the shield out of two or four separate pieces of metal that are formed and welded together. Such a shield structure 118 is shown in FIG. 4 herein where two formed C-shaped pieces 120 and 122 are welded along overlapping seams that extend parallel to the minor axis B--B. V-shaped notches are provided in the shield to extend the aperture 131 along the major axis A--A, and gussets 133 are formed adjacent to each of the V-notches to prevent deformation of the shield pieces 120 and 122. The welded multi-piece shield 118 is inherently stronger than the one-piece, bowl-like shields 18 and 18'; however, the shield 118 is more expensive to manufacture, since it requires the additional welding operation.